In an press release today, Microsoft has made the official announcement for the purchase of Skype — one the most expensive acquisitions to date according to the company. From the press release:

Microsoft Corp. (Nasdaq: "MSFT") and Skype Global S.à r.l today announced that they have entered into a definitive agreement under which Microsoft will acquire Skype, the leading Internet communications company, for $8.5 billion in cash from the investor group led by Silver Lake. The agreement has been approved by the boards of directors of both Microsoft and Skype.

... Skype will support Microsoft devices like Xbox and Kinect, Windows Phone and a wide array of Windows devices, and Microsoft will connect Skype users with Lync, Outlook, Xbox Live and other communities. Microsoft will continue to invest in and support Skype clients on non-Microsoft platforms.